Secondary containment panels and process for making and installing same

ABSTRACT

A method of manufacturing a plurality of secondary containment panels and assembling and installing the panels in a secondary containment system of an above-ground liquid storage tank or other retention facility includes forming a plurality of flexible substrate pieces. A liquid impermeable coating is applied to the upper surface of each piece such that an edge segment of the piece remains uncoated. The coating is applied to the substrate piece in an indoor enclosure. The coated pieces are delivered to the site of the tank and extended across the ground adjacent to the tank. At least a pair of the pieces are juxtaposed relative to one another such that a first one of the pieces overlaps the uncoated segment of the second piece to form a seam. An adhesive substance is then applied to the seam to fasten the first and second pieces together.

FIELD OF THE INVENTION

This invention relates to a process for manufacturing secondarycontainment panels of the type used in connection with above-ground fueland chemical storage tanks, as well as retention ponds and similarfacilities. The panels are first manufactured offsite in anenvironmentally controlled facility and then assembled and installedonsite to provide secondary containment in the event of spills or leaks.

BACKGROUND OF THE INVENTION

Above-ground petroleum storage tanks, chemical storage tanks and similarfacilities typically utilize a secondary containment system forcapturing hazardous liquid that leaks or spills from the tank. Secondarycontainment is also used for retention ponds, lakes and similarfacilities to prevent polluting substances such as drill water, acids,gasses and unsafe chemicals from entering the water table. Conventionalsecondary containment systems employ an impermeable or impervious linerthat extends across a basin or retention area. The liner, which isdesigned to prevent petroleum, chemicals or other hazardous materialsfrom seeping into the ground, typically comprises a plurality ofjuxtaposed geotextile fabric panels. These panels are cut as required,arranged across the containment area and then sprayed with a polyureacoating that renders the panels impermeable to the passage of liquidsdischarged from the tank or otherwise held in the retention facility.

Assembling and installing secondary containment panels onsite presents anumber of problems. Most significantly, when the polyurea is sprayedonto the geotextile fabric in the field, a significant amount of theimpermeable coating is apt to be dissipated, lost and wasted due to windand/or rain. Outdoor weather conditions tend to complicate theapplication process considerably. In order to provide the completedpanels with a stippled, slip-resistant surface, the polyurea coatingmust be sprayed onto the geotextile fabric from a distance of aboutseveral feet or more. This separation causes at least some of thesprayed coating to dissipate and miss the fabric entirely, particularlyunder windy conditions. Indeed, in a typical secondary containmentsystem, as much as 25% of the coating material can be wasted when it isapplied outdoors and onsite.

An additional disadvantage accompanying conventional coating applicationprocedures is that large amounts of polyurea coating and affiliatedapplicator equipment must be transported to and from the secondarycontainment site. The coating itself is typically transported to thesite in 55 gallon drums. After the drums are emptied and the coatingapplied to the geotextile fabric, the drums must be removed fordisposal. In addition, bulky applicator equipment including pumps,hoses, etc. must be transported to and from the secondary containmentsite. All of this adds to the complexity and expense of installing thesecondary containment system.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide animproved and more efficient technique for manufacturing and installingsecondary containment panels.

It is a further object of this invention to provide a method forassembling and installing the liner of a secondary containment system,which significantly reduces the amount of polyurea coating material thatis lost and wasted during the installation.

It is a further object of this invention to provide a method formanufacturing secondary containment panels in an environmentallycontrolled indoor environment so that effective impervious panels arepre-made without being subjected to wind, rain and other adverse weatherconditions that tend to dissipate and waste coating material when thesecondary containment liner is manufactured outdoors and onsite.

It is a further object of this invention to provide a method formanufacturing, assembling and installing secondary containment panelsthat is far more efficient and cost effective than previous secondarycontainment installation techniques.

It is a further object of this invention to provide a method formanufacturing and installing secondary containment panels thatsignificantly reduces the inconvenience and expense normally involved intransporting impermeable coating material to the secondary containmentsite and disposing of the empty containers for the coating after thecoating has been applied.

It is a further object of this invention to provide a technique forassembling and installing secondary containment panels that reduces theneed for much of the equipment, including pumps and hoses, normallyrequired when the liner of a secondary containment system ismanufactured in the field and onsite and which also significantlyreduces the maintenance required for such equipment and costs associatedtherewith.

It is a further object of this invention to provide a method formanufacturing secondary containment panels that is simpler, moreefficient and less costly than previously known techniques.

It is a further object of this invention to provide a method formanufacturing the liner of a secondary containment system which reducesthe inefficiency and expense of transporting adhesive coating andassociated application equipment (e.g. hoses and pumps) to the storagetank site where the secondary containment system is being installed andwhich thereby significantly facilitates installation of the secondarycontainment system and, in particular, the liner of the system.

It is a further object of this invention to provide a method formanufacturing secondary containment panels that are easy to roll-up andtransport to a secondary containment site for onsite installation.

It is a further object of this invention to provide a method formanufacturing environmentally friendly secondary containment panels thatcan be repeatedly, conveniently and efficiently recycled and reused asneeded.

This invention results from a realization that the impervious liner of asecondary containment system may be installed much more efficiently andcost effectively, and with far less waste of impermeable coating (e.g.polyurea) by prefabricating the liner in discrete secondary containmentpanels. These panels are pre-made in an environmentally controlled,enclosed facility wherein the impermeable coating is applied to anunderlying substrate (e.g. geotextile fabric) without being subjected topotentially adverse outdoor conditions such as wind and rain. Thissignificantly reduces the amount of coating that is wasted as thecoating is sprayed or otherwise applied onto the fabric substrate. Bythe same token, the technique of this invention greatly lessens thecomplexity, expense and hassle normally involved with transporting drumsof polyurea coating and associated applicator equipment (pumps, hoses,etc.) to and from the site of the secondary containment system.

This invention features a method of manufacturing a secondarycontainment panel for use in a secondary containment system of anabove-ground liquid storage tank or other liquid retention facility. Aflexible, generally flat substrate piece is formed. A liquid impermeablecoating is applied to an upper surface of the substrate piece whileleaving an edge segment of the upper surface of the piece uncoated. Thecoating is applied to the piece inside an environmentally controlledenclosure.

In a preferred embodiment, the coating is sprayed onto the substratepiece. The substrate piece may include a geotextile fabric and thecoating may be polyurea. Typically, the coating is sprayed on thesubstrate piece from a distance sufficient to form a slip-resistantstippled surface on the upper surface of the piece.

This invention also features a method for manufacturing, assembling andinstalling a plurality of secondary containment panels for use in asecondary containment system. Each panel is manufactured in thepreviously described manner by coating respective substrate pieces in anenvironmentally controlled enclosure and providing each piece with anuncoated edge segment. After the coated substrate pieces defining thepanels are manufactured, those pieces delivered to the site of a storagetank or retention facility (e.g. lake or pond). The coated substratepieces are then extended across the ground adjacent to the tank and atleast a pair of pieces are juxtaposed relative to one another such thata bottom surface of a first one of the pieces overlaps the uncoated edgesegment of a second substrate piece to form a seam between the pieces.An adhesive substance is applied to the seam to secure the piecestogether. In particular, polyurea coating, two sided adhesive tape orother adhesives are introduced between the lower surface of the firstsubstrate piece and the uncoated edge segment of the second piece tofasten together the first and second pieces. Adhesive may also beapplied across the seams and to the upper surface of the overlappingsubstrate pieces.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Other objects, features and advantages will occur from the followingdescription of a preferred embodiment and the accompanying drawings, inwhich:

FIG. 1 is a perspective view of an above-ground liquid storage tankutilizing a secondary containment system featuring a liner comprisingsecondary containment panels manufactured in accordance with thisinvention;

FIG. 2 is a fragmentary perspective view of a section of a liquidstorage tank having a liquid retention berm formed about the tank; apair of secondary containment panels are juxtaposed about the tank andextend across the berm in accordance with this invention;

FIG. 3 is a diagrammatic view of a roll of geotextile fabric beingdeployed in order to manufacture the secondary containment panels inaccordance with this invention;

FIG. 4 is a diagrammatic view of a piece of geotextile fabric being cutand having a liquid impermeable coating applied thereto;

FIG. 5 is a simplified perspective view depicting the process of animpermeable coating such as polyurea being applied to an upper surfaceof a piece of geotextile fabric in an environmentally controlled indoorenclosure;

FIG. 6 is a plan view of a secondary containment panel manufactured inaccordance with the method of this invention;

FIG. 7 is a perspective view of a supply of secondary containment panelssupported upon a trailer for transport to a storage facility where thepanels are installed as part of a secondary containment system for thefacility;

FIG. 8 is a simplified perspective view depicting how a pair ofadjoining panels are juxtaposed and adjoined to form a liner of thesecondary containment system;

FIG. 9 is an elevational view of the juxtaposed panels prior tointerengagement of the panels; and

FIG. 10 is an elevational view of the panels after they have beenadhesively fastened together.

There is shown in FIG. 1 an above-ground storage tank T foraccommodating an environmentally sensitive and potentially hazardousliquid such as petroleum or various other types of chemicals. Althoughthe typical tank has a generally cylindrical configuration, theparticular size, shape, construction and type of tank are notlimitations of this invention. In the version illustrated herein, tank Tincludes a generally cylindrical tank shell 2 that is supported upon aconcrete ring wall or slab 4. It should be understood that variousalternative tank constructions may be utilized within the scope of thisinvention. It should also be understood that various types of liquidsmay be accommodated within tank T. Most commonly, such tanks areutilized to hold petroleum and assorted types of hydrocarbon fuels.Potentially hazardous chemicals are also stored in above-ground tanks ofthis type.

A secondary containment system 10 commonly is installed about tank T inorder to catch and retain liquid fuel or chemicals that have spilledfrom tank T due, for example, to a leak in the shell of the tank or inthe pipes or other equipment associated with the tank. Spills can alsobe caused by overfilling the tank. System 10 comprises a secondarycontainment liner 12 that extends across the ground surrounding tank T.The secondary containment system may also feature various othercomponents including sensors, alarms, switches and valves (not shown),which react to a liquid spill by shutting off further pumping of liquidinto the tank T and which notify the owner/operator of the spill so thatneeded repairs and other corrective action may be performed.

System 10 specifically includes an earthen berm 14 that encircles orotherwise surrounds tank T. As further shown in FIG. 2, berm 14comprises a liquid containment wall disposed upon and rising above theunderlying ground surface G. The berm defines a spill retention basin 15between tank T and berm 14. Berm 14 may comprise earthen material suchas native or outsourced soils. Alternatively, the berm may includereinforced concrete, steel sheets driven into underlying ground surfaceG, concrete blocks and/or asphalt. Berm 14 is typically configured in agenerally annular fashion about the tank as best shown in FIG. 1. It isbuilt at various select distances from the tank shell in order toprovide the needed containment capacity. Preferably, the berm is about5′-20′ from the outer wall of the tank shell, although this distance maybe varied. Berm 14 is constructed to have a height of approximately12″-24″, although such height may again be varied to provide the neededsecondary containment capacity about the tank. As best shown in FIG. 2,berm 14 has a sloped inner wall 16 generally facing tank T. Berm 14 mayinclude various other non-annular configurations suited to conform tothe area about the tank available for secondary containment. It is onlynecessary that the berm peripherally surround the tank so that spilledfuel is retained within the basin defined by the berm. The precise shapeof the berm may be varied within the scope of this invention.

A trench 21, FIGS. 1 and 2, is disposed annularly about tank T radiallyoutwardly of berm 14 and immediately adjacent to the berm. This trench,which is optional, helps to securely retain impermeable liner 12 withinthe spill retention basin. Liner 12 extends across basin 15 and, inparticular, covers berm 14 and the intermediate ground surface G formedbetween tank T and berm 14. Liner 12 typically comprises a flexiblegeotextile fabric sheet that is constructed of an industrial fabriccomposed of woven fibers. Alternative materials may be substitutedwithin the scope of the invention. The sheet forms a substrate to whicha liquid polyurea coating layer impermeable to liquids is spray coatedor otherwise applied. Alternative types of impermeable coatingsmaterials may also be used. In the event of an accidental leak, overfillor spill of fluid, impermeable liner 12 captures the leaked fluid andretains it within the basin 15 so that the environmentally hazardousliquid does not seep into the ground and underlying water table.

The foregoing secondary containment construction is largelyconventional. Typically, the liner is constructed and installed byconfiguring sheets of the geotextile fabric about the storage tank sothat the sheets extend across the ground and cover the area defining thespill retention basin, as well as the berm and trench. The impermeablecoating is then sprayed onto the fabric and allowed to cure. Aspreviously described, this procedure has presented several problems.Governmental regulations have commonly required that the upper surfaceof the liner be stippled to provide a non-skid/slip surface. Toaccomplish this, the polyurea coating material must be sprayed onto theupper surface of the geotextile fabric in a pattern achieved only byholding the nozzle of the sprayer a distance of about several feet fromthe fabric. As a result, when the coating is sprayed in the field andonsite, it tends to dissipate in the outdoor environment. A considerableamount of coating material (e.g. up to 25%) can be lost and wasted,especially when windy, rainy or other adverse weather conditions areencountered. In addition, significant quantities of coating material,which is typically stored in 55 gallon drums, must be transported to thesite of the storage tank. After the coating is applied, the empty drumsmust be removed and discarded. Applicator equipment including pumps andhoses must also be transported to and from the site. All of this addssignificantly to the inconvenience and cost of installing the secondarycontainment system.

The present invention overcomes the foregoing problems. As shown in FIG.1, liner 12 includes a plurality of secondary containment panels 24 thatare individually manufactured, in accordance with this invention, beforethey are delivered to the site and assembled. A representative pair ofadjoining panels 24 a and 24 b are depicted in FIG. 2 and described morefully below.

A critical aspect of this invention is that the secondary containmentpanels are manufactured individually in an environmentally controlledindoor environment prior to delivery to the site of the storage tank. Asshown in FIG. 3, a selected length of flexible geotextile fabricsubstrate 30 is unwound in the direction of arrow 34 from a supply roll32 of such material. Typically, such fabric is available in rectangulardimensions. The width of the substrate and the selected length deployedfrom roll 32 may be varied widely within the scope of the invention. Forexample, the width of the substrate may be approximately 12′. Variousalternative lengths (e.g. 30′, 60′, 80′) may be selected to becompatible with the size of the secondary containment system that isbeing constructed for a particular tank. Various alternative widths mayalso be employed. As shown in FIG. 4, when a desired length of fabrichas been deployed, the fabric is transversely cut by a standard cuttingmachine or tool 40 to produce a rectangular substrate piece 42.Additional substrate pieces are formed in an analogous fashion.

After piece 42 has been produced, polyurea coating 44 is sprayed ontothe upper surface of piece 42 by a conventional sprayer 46. As shown inFIG. 5, it is important that this spray application be performed in anenvironmentally controlled indoor enclosure 50, which may comprise afactory, warehouse or other manufacturing facility. As shown therein,worker W holds an applicator hose H and directs an applicator nozzle Nat the upper surface of substrate piece 42. Hose H is operably connectedto a conventional applicator pump and supply of polyurea or othercoating (not shown). The worker operates the applicator equipment tospray polyurea 44 onto the upper surface of substrate piece 42 in themanner shown in FIGS. 4 and 5. In particular, the worker proceedsgenerally from the leading end of piece 42 to the trailing end andsprays the polyurea onto the geotextile fabric in a reciprocatingpattern 52, FIG. 4. The layer of polyurea 44 is normally applied atapproximately 80 mils dry-film thickness. Other thicknesses may be usedwithin the scope of this invention. Worker W holds the tip of nozzle N asufficient desired distance (e.g. 3′) from the upper surface of piece 42so that a non-slip stippled finish or pattern is formed by coating 44 onsubstrate piece 42. While applying the coating, worker W should becareful to leave an uncoated edge segment 58 about some or all of theperiphery of piece 42. This uncoated edge segment may be left about theentire perimeter of piece 42 or only along one side or other edgesegment of the substrate piece. The uncoated edge segment facilitatesadhesion of the substrate to an overlapping adjoining piece when thesubstrate pieces are assembled and installed at the storage tank site.

When worker W reaches a selected short distance from the trailing edgeof substrate piece 42, application of coating 44 is completed. Thecoating is then allowed to cure so that a completed secondarycontainment panel 24, shown in FIG. 6, is formed. That panel comprisesthe underlying flexible substrate piece 42 and the applied impermeablecoating material 44, which defines a stippled texture. Uncoated edgeregion 58 surrounds coated upper surface 44. As previously indicated,the uncoated edge segment extends at least partially about the peripheryof panel 24. The completed panel maintains its flexibility and is easyto roll-up so that it can be compactly and conveniently transported to adesired installation site.

In alternative embodiments, the coating material may be sprayed onto orotherwise applied to the substrate pieces by various other meansincluding robotic applicators and alternative machines. The manner inwhich the coating is applied is not a limitation of this invention.

After a desired number of panels 24 required for a particular job aremanufactured in the foregoing manner, they are transported to thestorage tank site or other liquid retention site by various means oftransportation. For example, as shown in FIG. 7, a number of panels 24are draped across or stacked upon a trailer 70 that is pulled by anappropriate delivery vehicle (not shown). The flexible panels may alsobe quickly and conveniently rolled-up and stacked in the deliveryvehicle. When the panels arrive at the site, they are unloaded, unrolledif necessary, and arranged about the periphery of tank T as shown inFIGS. 1 and 2. Individual panels 24 may be cut as needed to accommodateand conform to the tank and equipment such as pipes and machineryassociated with the tank. For example, as best shown in FIG. 2,individual panels such as representative panels 24 a and 24 b areoriented to extend longitudinally from tank ring wall 13 (which thepanels overlap) across the ground G defining basin 15 and berm 14. Thedistal end of each panel 24 a and 24 b is disposed in trench 21. Variousother configurations and orientations may be employed within the scopeof this invention. The individual panels may be arranged and juxtaposedin any manner and orientation needed to provide substantially completeliner coverage over basin 15 and the ground area surrounding tank T.Substantially complete coverage is required so that the liner willadequate capture and retain any liquid that accidentally spills or leaksfrom the tank.

After the panels 24 are arranged and stretched out across the groundsurrounding the tank, adjoining panels are fastened together to from theliner of the secondary containment system in the manner shown in FIGS. 2and 8-10. In particular, as represented by adjoining panels 24 a and 24b, respective edge segments 58 of these panels are overlapped to form aseam 85. The longitudinal left-hand edge 80 of underlying panel 24 b isdisposed beneath panel 24 a as shown in FIG. 2 and 8-10. The adjoiningpanels are then adhesively joined by introducing an adhesive substancebetween the overlapping edge segments 58 as indicated by arrow 82 inFIG. 8. This adhesive substance may comprise a two sided tape 86, FIG.10, or alternatively various types of glues, epoxies or other forms ofadhesive. Polyurea coating or alternative types of coating materials mayalso be introduced between the overlapping panels. In either case, theoverlapping edge segments of respective panels 24 a and 24 b are pressedtogether as indicated by opposing arrows 88 in FIG. 9. Finally, asdepicted in FIG. 10, coating material is sprayed by sprayer 87 acrossthe upper surface of seam 85 and typically onto the adjacent sections ofpanels 24 a and 24 b. This seals and securely fastens together theadjoining panels. A similar interengagement and interconnection is madebetween each of the other panels 24 of the secondary containment liner12.

In contrast, to prior liner installation techniques, application ofpolyurea coating onsite is generally limited to regions of the seamsalong the seams or joints formed between the adjoining panels. The linerthus requires the application of far less coating in the field than isconventionally required when the entire liner is spray coated withpolyurea as is performed in the prior art. Because much less coating isapplied onsite, there is far less waste of such material. In addition,less coating material, fewer storage tanks and less related applicatorequipment need to be transported to and from the installation site.

In alternative embodiments, panels 24 may be assembled and installed inan analogous manner in applications such as retention ponds and lakesand “frac” containment facilities. The panels are constructed andinstalled in the manner previously described and achieve correspondingadvantages to those described in the storage tank embodiment.

The panels are environmentally friendly and can be reused and recycledas needed. When use of the assembled panels is no longer required at aparticular containment site, the liner can be cut along the seams orotherwise to form reusable panels. These used panels can then beconveniently rolled-up and transported to a new containment site wherethey can be re-seamed and/or reassembled with newly manufactured panels(made as previously described) and reinstalled as a new secondarycontainment liner. This technique saves materials and cost and improvesefficiency considerably.

Accordingly, the system of the present invention allows for secondarycontainment liners to be assembled and installed much more efficientlythan has been done previously. Because the coating is applied in anenvironmentally controlled indoor site, far less material is wasted.Production costs are thereby significantly reduced. By the same token,much less coating material and related application equipment is requiredat the site of the storage tank. Transportation costs and inconvenienceare thereby significantly reduced. In addition, the cost and annoyanceassociated with delivering 55 gallon drums of coating to the job siteand then disposing of those drums after installation of the secondarycontainment system is completed are reduced significantly.

From the foregoing it may be seen that the apparatus of this inventionprovides for a process for manufacturing secondary containment panels ofthe type used in connection with above-ground fuel and chemical storagetanks. While this detailed description has set forth particularlypreferred embodiments of the apparatus of this invention, numerousmodifications and variations of the structure of this invention, allwithin the scope of the invention, will readily occur to those skilledin the art. Accordingly, it is understood that this description isillustrative only of the principles of the invention and is notlimitative thereof.

Although specific features of the invention are shown in some of thedrawings and not others, this is for convenience only, as each featuremay be combined with any and all of the other features in accordancewith this invention.

Other embodiments will occur to those skilled in the art and are withinthe following claims:

1. A method of manufacturing and assembling a plurality of secondarycontainment panels for use in a secondary containment system, saidmethod comprising: forming a plurality of flexible substrate pieces;applying to an upper surface of each said piece a liquid impermeablecoating such that an edge segment of said piece remains uncoated, thecoating being applied to the upper surface of the substrate piece in anenvironmentally controlled enclosure; juxtaposing at least a pair ofsaid coated pieces relative to one another such that a lower surface ofa first one of said pieces overlaps an uncoated edge segment of a secondsaid piece to form a seam; and spraying an adhesive substance to saidseam to fasten together said first and second pieces.
 2. The method ofclaim 1 in which said coating is sprayed onto the upper side of saidsubstrate in an indoor enclosure wherein wind and rain are substantiallyrestricted from dissipating or otherwise affecting the coating as it issprayed.
 3. The method of claim 1 in which said adhesive substance isintroduced between said lower surface of said first piece and saiduncoated edge segment of said second piece and the overlapping piecesare pressed together.
 4. The method of claim 1 in which said adhesivesubstance is applied across said seam and to the upper surfaces of eachof said first and second pieces.
 5. The method of claim 1 in which saidadhesive substance includes polyurea coating.
 6. The method of claim 1in which said adhesive substance includes a two sided tape interposedbetween said overlapping pieces.
 7. A method of manufacturing aplurality of secondary containment panels and assembling and installingsaid panels in a secondary containment system, said method comprising:forming a plurality of flexible substrate pieces; applying to an uppersurface of each substrate piece a liquid impermeable coating such thatan edge segment of said piece remains uncoated, the coating beingapplied to the substrate piece in an environmentally controlledenclosure remote from the site of the system; delivering the coatedsubstrate pieces to the site of the system; extending the coatedsubstrate pieces across the ground and juxtaposing at least one pair ofthe pieces relative to one another such that a first one of the piecesoverlaps the uncoated segment of a second substrate piece to form aseam; and applying an adhesive substance to said seam to fasten thefirst and second pieces together.
 8. The method of claim 7 wherein saidsubstrate piece includes a geotextile fabric.
 9. The method of claim 7wherein the impermeable coating includes polyurea.
 10. The method ofclaim 9 further including spraying the coating onto the upper side ofthe substrate piece at a sufficient distance from the piece to produce astippled, slip-resistant texture.
 11. The method of claim 9 in whichsaid adhesive substance is introduced between said lower surface of saidfirst piece and said uncoated edge segment of said second piece and theoverlapping pieces are pressed together.
 12. The method of claim 9 inwhich said adhesive substance is applied across said seam and to theupper surfaces of each of said first and second pieces.
 13. The methodof claim 9 in which said adhesive substance includes polyurea coating.14. The method of claim 9 in which said adhesive substance includes atwo sided tape interposed between said overlapping pieces.
 15. A methodof manufacturing a secondary containment panel for use in the secondarycontainment system, said method comprising: forming a flexible,generally flat substrate piece; applying a liquid impermeable coating toan upper surface of said piece while leaving an edge segment of theupper surface of said piece uncoated, the coating being applied to thepiece inside an environmentally controlled enclosure.
 16. The method ofclaim 15 in which the coating is sprayed onto the substrate piece. 17.The method of claim 15 in which said substrate piece includes ageotextile fabric.
 18. The method of claim 15 in which said coatingincludes polyurea.
 19. The method of claim 16 in which said coating issprayed onto said substrate piece from a distance sufficient to form aslip-resistant stippled surface on the upper surface of the piece.
 20. Asecondary containment panel manufactured in accordance with the methodof claim 15.